Field of the Invention
Embodiments of the present invention generally relate to a method and apparatus for temporarily sealing a bore of a tool. More particularly, the invention relates to a ball seat and a method and apparatus for remotely releasing the ball.
Description of the Related Art
In the completion and operation of a hydrocarbon well, it is often necessary to remotely actuate a downhole tool in order to move the tool from a first to a second state. In one example, a packer is run into the well on a string of tubulars and then actuated, thereby causing sealing members to extend radially outwards into sealing contact with walls of the wellbore. One way of remotely actuating the tool is through a temporary increase in fluid pressure adequate to shift a piston formed on the tool that in turn causes the sealing members to move. In order to increase pressure in the area of the tool, the wellbore is typically blocked at a location below the tool. In one instance, the wellbore is blocked with a ball and ball seat. In one example, a ball is dropped from the surface of the well into the ball seat. With the bore blocked, pressure is increased to a point that sets the tool. Thereafter, pressure is increased to a higher level in order to “blow out ” the ball seat, permitting the ball to fall through the seat and the bore to be re-opened. While the forgoing arrangement is operable, it necessarily requires high pressures, especially to blow out the ball seat. High pressure can damage hydrocarbon-bearing formations through shock loading due to pressure surge or water hammer effect.
There is a need therefore, for a ball and seat arrangement wherein the ball can be released from the seat without the use of a fluid pressure differential across the seat.